The present invention relates to a home laundry drier.
More specifically, the present invention relates to a rotary-drum home laundry drier comprising: a substantially parallelepiped-shaped outer box casing; a cylindrical bell-shaped drum for housing the laundry to be dried, and which is located in axially rotating manner inside the casing to rotate about its horizontally oriented longitudinal axis, directly facing a laundry loading and unloading opening formed in the front face of the casing; a door hinged to the front face of the casing to rotate to and from a rest position closing the opening in the front face of the casing to seal the casing and the bell-shaped drum.
Further, a rotary-drum laundry drier of the above type comprises a closed-circuit, a hot-air generator designed to circulate inside the revolving drum a stream of hot air with a low moisture content, and which flows through the revolving drum and over the laundry inside the drum to rapidly dry the laundry.
In the rotary-drum laundry drier of the above type, the closed-circuit, hot-air generator comprise an air recirculating conduit having its two ends connected to the revolving drum, on opposite sides of the latter; a centrifugal fan located along the recirculating conduit to produce, inside the latter, an airflow which flows through the revolving drum; and finally a heat-pump device having: a compressing device, which subjects a gaseous refrigerant to compression (e.g. adiabatic compression) so that refrigerant pressure and temperature are much higher at the outlet than at the inlet of compressing device; and two heat exchangers, which are located one after the other, along the air recirculating conduit, and are designed to receive the refrigerant from the compressing device so that to cool or heat the airflow.
In detail, a first air/refrigerant heat exchanger, commonly referred to as the evaporator, provides for rapidly cooling the airflow arriving from the revolving drum to condense the surplus moisture in the airflow; whereas a second air/refrigerant heat exchanger, commonly referred to as the condenser, provides for rapidly heating the airflow arriving from the first heat exchanger and directed back to the revolving drum, so that the airflow re-entering into the revolving drum is heated rapidly to a temperature higher than or equal to that of the air flowing out of the revolving drum.
In the above domestic laundry driers, flowing of the airflow through the revolving drum is accomplished by an electrical motor, i.e. a three-phase induction electric motors that drives both the centrifugal fan and a transmission system that rotates the revolving drum.
Unluckily, despite the fact that there are several removable air-filters located in the air recirculating conduit, during the flowing of the air through the revolving drum, particles of lint/fluff/dust build up inside of the first and second air/refrigerant heat exchanger, causing a gradual clogging up of the closed-circuit which creates loss of pressure inside the air recirculating conduit.
As a result of the loss of pressure inside the recirculating conduit, the rotation speed of the centrifugal fan and the flow rate of the air flow tend to gradually decrease, causing the drawback that the drying time increases and, consequently, the drying process slows down.
Due to the fact that the rotation speed of the centrifugal fan decreases, the electric motor is subjected to slow down and works under stress causing disadvantageous higher electricity power consumption.
In addition, the air temperature inside the heat pump assembly tends to gradually increase, reaching a high value which may both cause damage to the clothing and several heat dissipation problems at the compressing device of the heat-pump device.
In detail, in that event, the heat-pump device needs to operate at full capacity, but the compressing device may not be able to absorb by means of the evaporator a sufficient amount of heat from the airflow so as to maintain the air temperature in the air recirculating conduit under a safety threshold over which the compressing device is automatically turned off by an auxiliary safety dryer device.
Finally, it should be understood that when the compressing device operates in the full capacity state, it becomes quite noisy and unfortunately its operating life decreases.